There are well known issues as regards the necessity of providing a device for adjusting the useful length of a bracelet.
On the one hand, in the case of bracelets formed of links, the value of the user's wrist circumference may fall between two configurations of the bracelet separated from each other by a single link. This is also the case when a bracelet made of leather, rubber or the like has perforations that do not allow for a sufficiently fine adjustment. Similarly, it is useful to provide a device for adjusting the useful length of the bracelet that will allow for a finer adjustment of the bracelet length than the removal or addition of a link.
Further, it is also known that the value of the wrist circumference varies with the season, with the maximum value generally being attained in summer and the minimum value being attained in winter. Here too, it is preferable to provide a fine adjustment device for the useful length of the bracelet that enables the person wearing the bracelet to adjust the length to improve the wear comfort of the bracelet.
By way of example, EP Patent Application No 0913106 A1 discloses a clasp with a buckle of the unfolding type comprising a cover with a series of pairs of holes intended to accommodate the ends of a bar for attaching a bracelet. Two adjacent pairs of holes are separated by a distance defining one adjustment step of the useful bracelet length, to answer the aforementioned problems.
However, adjustment of the length of the corresponding bracelet is difficult because it cannot be performed without using a pointed tool. Not only does this operation require a certain dexterity, but it also risks causing damage to the cover if the person performing the adjustment is clumsy.
To avoid this situation, alternative devices have already been disclosed, such as for example in EP Patent No 0350785 B1 which discloses a similar clasp to the above but comprising, by way of alternative, a device for adjusting the useful length of the bracelet that can be operated without using a tool. Indeed, the clasp disclosed in that Patent is of the type with an unfolding buckle comprising two strips hinged to each other by means of a pin that passes through both, each of the strips carrying at the free end thereof a member for fastening a bracelet. A first strip bears a hook intended to be engaged in a hole arranged in the second strip to cooperate therein with a spring catch that enables the hook, and thus the clasp, to be locked in a closed state. The second strip comprises two parts that are slidable in relation to one another within a certain predefined range, defining an adjustment step of the useful length of the bracelet. A first of these two parts bears the hinge connecting it to the first strip, while the second part bears the locking spring catch. The hole in which the hook engages to lock the clasp has a length, in the longitudinal direction of the bracelet, which equates to the sliding range between the two parts of the second strip. The spring catch has a central part defining two positions for the hook in the longitudinal direction of the bracelet that correspond to two different useful lengths of the bracelet. A control member comprising, in particular, a push-piece allows actuation of the spring catch to release the hook and open the clasp.
Thus, the clasp described in this Patent has to be open in order to proceed with the length adjustment.
It may be pointed out that a resulting drawback thereof is that the adjustment of the bracelet length is lost each time the clasp is opened. Consequently, each time the clasp is closed, the wearer of the bracelet has to check that the hook is inserted on the side of the central spring catch part matching the desired bracelet length.
Adjustment devices comprising a specific locking member have also been proposed, by way of alternative, to avoid this type of drawback.
EP Patent Application No 1378185 A1 provides an example thereof. However, these devices generally have complex and not very discrete structures since they can comprise at least one control member associated with the locking of the clasp and at least one additional control member associated with the locking of the adjusting device.